Log Message:
www/aws: Fix build for different zlib and libssl locations

The configuration for the location of libz and libssl both were wrong,
and they were corrected with their respective BUILDLINK_PREFIX.

In addition, regardless of where libssl is located, the standard location
(/usr/include) was searched instead of relative to the library.  This
required a patch to the GPR build in order to pass -I<loc> to the
compilation of C files.

The unnecessary removal of empty directories was removed as SunOS find
does not support the -empty switch.

Tested on Joyent dev area where both libz and libssl are not at /usr/lib.